Nerve Regeneration: Tissue Engineering Strategies

Abstract

The nervous system of the adult mammal is divided into two main components: the peripheral nervous system (PNS) and central nervous system (CNS). The PNS, consisting of cranial and spinal nerves and their associated ganglia, has the intrinsic ability for repair and regeneration. However, the adult mammalian central nervous system (CNS), consisting of the brain and spinal cord, is viewed as largely incapable of selfrepair or regeneration of correct axonal and dendritic connections after injury [1-3]. When a peripheral nerve is injured and the nerve retracts, or tissue is lost, preventing an end-to-end repair, grafting is a commonly performed. Grafting methods, involving autografts and allografts, provide trophic factors and guidance for regenerating axons [4,5]. However, there are major limitations to grafting including multiple surgeries, lack of donor tissue, and immune rejection. The CNS is a more complex environment that proves to be not as amenable to healing as the PNS. Adult CNS injury is typically followed by neuronal degeneration, cell death, and the breakdown of synaptic connections. It is established that fish, amphibia, mammalian peripheral nerves as well as developing central nerves respond differently to injury than the adult mammalian CNS. In these systems, functional axons can regrow after they have been damaged [1]. However, currently, in the mammalian CNS, there is no treatment for the restoration of human nerve function due to the intricate series of events that must take place in order for regeneration to occur.